A dependence of the tidal disruption event rate on global stellar surface mass density and stellar velocity dispersion

Or Graur*, K. Decker French, H. Jabran Zahid, James Guillochon, Kaisey S. Mandel, Katie Auchettl, Ann I. Zabludoff

*Corresponding author for this work

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The rate of tidal disruption events (TDEs), RTDE, is predicted to depend on stellar conditions near the super-massive black hole (SMBH), which are on difficult-to-measure sub-parsec scales. We test whether RTDE depends on kpc-scale global galaxy properties, which are observable. We concentrate on stellar surface mass density, ΣM⋆, and velocity dispersion, σv, which correlate with the stellar density and velocity dispersion of the stars around the SMBH. We consider 35 TDE candidates, with and without known X-ray emission. The hosts range from star-forming to quiescent to quiescent with strong Balmer absorption lines. The last (often with post-starburst spectra) are overrepresented in our sample by a factor of 35+21−17 or 18+8−7, depending on the strength of the Hδ absorption line. For a subsample of hosts with homogeneous measurements, ΣM⋆=109-1010 M⊙/kpc2, higher on average than for a volume-weighted control sample of Sloan Digital Sky Survey galaxies with similar redshifts and stellar masses. This is because: (1) most of the TDE hosts here are quiescent galaxies, which tend to have higher ΣM⋆ than the star-forming galaxies that dominate the control, and (2) the star-forming hosts have higher average ΣM⋆ than the star-forming control. There is also a weak suggestion that TDE hosts have lower σv than for the quiescent control. Assuming that RTDE∝ΣαM⋆×σβv, and applying a statistical model to the TDE hosts and control sample, we estimate α^=0.9±0.2 and β^=−1.0±0.6. This is broadly consistent with RTDE being tied to the dynamical relaxation of stars surrounding the SMBH.
Original languageEnglish
Article number39
Number of pages19
JournalThe Astrophysical Journal
Publication statusPublished - 22 Jan 2018
Externally publishedYes


  • astro-ph.HE
  • astro-ph.GA


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